Niger's government has arrested nine military officers for planning a coup, the interior minister said Saturday. The move more than doubles the number of arrests reported earlier this week.

President Mahamadou Issoufou said in a televised address Thursday the alleged conspirators had planned to use aerial firepower and had prevented the movement of military assets from the capital, Niamey, to the southern region of Diffa.

Issoufou was elected in 2011, a year after a coup, and is running for a second term in elections scheduled for Feb. 21. Political tension is already high, with critics accusing him of repression and expressing doubts about the latest coup claims.

"Nine officers identified as responsible for the attempted coup have been arrested and will be presented before a military court," Interior Minister Hassoumi Massaoudou told reporters.

Massaoudou said a second lieutenant who had fled turned himself in to gendarmes.

Military sources and family members had previously said four senior officials were arrested, including the former military chief of staff, Gen. Souleymane Salou, and Lt. Col. Dan Haoua, who headed Niamey's air force base.

Political opponents said they did not believe the government's claims.

"We don't see any evidence of the attempted coup," said opposition leader Amadou Boubacar Cisse. "Rather, he (Issoufou) has created a lot of problems around the election and has taken fraudulent actions with the electoral list."

In December the government announced it would audit its voter registry before the presidential election after demands lodged by opposition parties.